The making of electrical connections between electronic components has long been accomplished using printed circuit boards (PCBs). The first such circuit boards had only a single routing layer on a top surface thereof for routing electrical signals between electronic components mounted thereon. These single routing layer circuit boards have severe limitations with regard to the number of electrical signals that can be routed between electronic components mounted on the same circuit board. That is, the number of electrical signals that can be routed between electronic components mounted on a single routing layer circuit board is limited by the amount of area on the single routing layer.
The area limitations associated with single routing layer circuit boards led to the development of multilayer PCBs. Such multilayer PCBs may be either single or double-sided and may have multiple routing layers on the surface of and buried within the multilayer PCBs. Thus, such multilayer PCBs have allowed a large increase in the number of electrical signals that may be routed between electronic components mounted on the same circuit board.
The use of multilayer PCBs has been particularly beneficial when using electronic components having high-density packages. That is, electronic components having high-density packages generally require multiple layers of a multilayer PCB to make electrical connections with other electronic components mounted on the same circuit board. In fact, the density of electronic component packages typically dictates the number of layers that must be provided by the multilayer PCB upon which the electronic components are mounted. While the number of layers that may be provided by a multilayer PCB is theoretically unlimited, reliability and other problems occur when the number of layers in a multilayer PCB exceeds a reasonable number, particularly when trying to route high-speed electrical signals between electronic components. For example, when making electrical connections between different layers in multilayer PCBs, a combination of electrically conductive traces and electrically conductive vias are generally used. While electrically conductive vias allow direct vertical electrical connections to be made between different layers within a multilayer PCB, there are intrinsic parasitics associated with these electrically conductive vias that can adversely affect the performance of signals propagating therethrough. That is, these electrically conductive vias have intrinsic parasitic resistance, capacitance, and inductance, which can adversely affect signals propagating along each electrically conductive via. In addition, these intrinsic parasitics can also have an adverse effect on the manufacturability of a PCB and thus the cost thereof. Because of their adverse affect on signal performance, these intrinsic parasitics can also limit the bandwidth of signals propagating along each electrically conductive via. These adverse affects only increase as the number of layers in a multilayer PCB increase.
To alleviate at least some of the above-mentioned adverse effects, it is often helpful to have resistive, capacitive, and/or inductive components electrically connected in series and/or parallel with an electrically conductive via, which is also electrically connected to a signal driver contact of an electronic component. However, this if often difficult to achieve since the signal driver contact may be located within the interior of a contact array of the electronic component, and thus there is no place to mount the resistive, capacitive, and/or inductive components. Even if the signal driver contact is located along the periphery of a contact array of the electronic component, there may still be no place to mount the resistive, capacitive, and/or inductive components since electronic components are now being placed ever closer together on the surfaces of PCB's and other types of multilayer signal routing devices.
One proposed solution to the problem of mounting resistive, capacitive, and/or inductive components since electronic components near a signal driver contact of an electronic component is to bury or embed the resistive, capacitive, and/or inductive components within a PCB or other type of multilayer signal routing device. However, the cost and maturity of suitable technologies for this proposed solution make it impractical.
In view of the foregoing, it would be desirable to provide a technique for mounting resistive, capacitive, and/or inductive components on a multilayer signal routing device near a signal driver contact of an electronic component that overcomes the above-described inadequacies and shortcomings.